Generally, a method of manufacturing a pouch-type secondary battery includes the steps of injecting an electrolyte through an electrolyte injection portion located at one side of a rim region of a prepared pouch-type secondary battery, primarily sealing the electrolyte injection portion along a primary sealing line and then performing charging/discharging, cutting a part of the electrolyte injection portion along a cutting line located at an inner side of the primary sealing line, performing degassing, secondarily sealing the electrolyte injection portion, and cutting a part of the electrolyte injection portion along a cutting line located at an outer side of the secondary sealing line.
In addition, after the pouch is completely formed, a cutting process is performed to cut unnecessary portions of the edge area of the pouch.
However, as shown in FIG. 1, generally, when a pouch-type secondary battery 1 is completely cut, at least one corner is bent due to a stress remaining at the edge of the pouch to cause a curling portion 2, thereby deteriorating the product quality.
In relation to this problem, in order to prevent the problem that the pouch is rolled up due to the forming pressure, Patent Literature 1 discloses a vacuum adsorption positioning forming mold, which vacuum-absorbs an aluminum pouch to allow satisfactory positioning when the aluminum pouch used for manufacturing a cellular phone battery is formed and cut.
As another alternative, Patent Literature 2 directed to improving the warping phenomenon in a manufacturing process discloses a pouch exterior for a secondary battery and its manufacturing method, which has an accommodation portion in which an electrode assembly is accommodated and a groove is additionally formed along an edge region of the pouch exterior.
However, the conventional techniques related to solving the curling problem of the pouch have a complicated device structure and may not be universally applied to a pouch-type secondary battery manufacturing process.